Lau Ernest W, Bonnemeier Hendrik, Baldauf Benito
Department of Cardiology, Royal Victoria Hospital, Belfast, United Kingdom.
Department of Cardiology, University Rostock, Rostock, Germany; Medical Faculty, Christian-Albrechts-University, Kiel, Germany; Division of Life Sciences, University of Applied Sciences, Bremerhaven, Germany.
Heart Rhythm. 2025 Jul;22(7):e229-e236. doi: 10.1016/j.hrthm.2024.12.038. Epub 2024 Dec 30.
Left bundle branch block (LBBB) causes immediate electrical and mechanical dyssynchrony of the left ventricle (LV) and gradual structural damages in the Purkinje cells and myocardium. Mechanical dyssynchrony reduces the LV ejection fraction (EF) instantly, but only to ≈55% in an otherwise normal heart. Because of the heart's in-built functional redundancy, a patient with LBBB does not always notice the heart's reduced efficiency straightaway. After a variable period of time (which could be from days to decades), the patient may become symptomatic with heart failure (HF), which classifies as HF with preserved EF ≥50% (HFpEF). The LVEF drops further because of continuous adverse remodeling and inefficient cardiac contraction. The patient transits to HF with moderately reduced EF 35%-50% (HFmrEF) and then reduced EF ≤35% (HFrEF) over 5-21 years. Cardiac resynchronization therapy (CRT) is currently only indicated in guidelines for HFrEF and LBBB. LBBB shortens the median survival of patients with HFmrEF by 5.5 years. Randomized controlled trials have shown that CRT improves echocardiographic indices for HFmrEF with LBBB. CRT in HFpEF with LBBB is a promising but underexplored/underused therapy. There have been anecdotal reports that CRT produced symptom relief in patients debilitated by HFpEF with LBBB, who constitute ≈6% of all patients with HF and an adequate pool of potential randomized controlled trial participants. Conduction system pacing in the form of left bundle branch area pacing is an emerging pacing strategy that might reverse and forestall the deleterious effects of LBBB.
左束支传导阻滞（LBBB）会立即导致左心室（LV）出现电和机械不同步，并使浦肯野细胞和心肌逐渐发生结构损伤。机械不同步会立即降低左心室射血分数（EF），但在其他方面正常的心脏中，仅降至约55%。由于心脏固有的功能冗余，LBBB患者并不总是能立即察觉到心脏效率的降低。经过一段可变的时间（可能从数天到数十年）后，患者可能会出现心力衰竭（HF）症状，这种情况归类为射血分数保留的心力衰竭（HFpEF），即EF≥50%。由于持续的不良重塑和心脏收缩效率低下，左心室射血分数会进一步下降。在5至21年的时间里，患者会转变为射血分数中度降低的心力衰竭（HFmrEF），即EF为35% - 50%，然后转变为射血分数降低的心力衰竭（HFrEF），即EF≤35%。目前，心脏再同步治疗（CRT）仅在HFrEF和LBBB的指南中有指征。LBBB会使HFmrEF患者的中位生存期缩短5.5年。随机对照试验表明，CRT可改善LBBB合并HFmrEF患者的超声心动图指标。LBBB合并HFpEF患者的CRT是一种有前景但尚未充分探索/使用不足的治疗方法。有一些轶事报道称，CRT可使因LBBB合并HFpEF而虚弱的患者症状得到缓解，这些患者约占所有心力衰竭患者的6%，是潜在随机对照试验参与者的充足来源。以左束支区域起搏形式的传导系统起搏是一种新兴的起搏策略，可能会逆转并预防LBBB的有害影响。
